Process analysis and implementation points for heat treatment of automobile leaf springs using high-frequency induction heating equipment

The automobile leaf spring is an elastic element. Its function is to withstand the effects of the cabin and the load (static load). It can transfer vertical loads, alleviate and suppress the impact caused by uneven road surfaces. Therefore, during the operation of the car, the leaf spring To withstand huge friction, in order to meet the needs of its work, many manufacturers use high-frequency induction heating equipment for heat treatment, and the effect is very good. Today, let’s take a look at the analysis and implementation points of the heat treatment process of leaf springs.

(1) At present, some spring factories adopt high-temperature rapid tempering process. That is, high-frequency induction heating equipment is used for heating. At this time, the surface of the steel plate is around 600°C. Therefore, the tempering time is shortened, the martensite decomposition speed is accelerated, and the quenching stress is eliminated. The carbides decomposed by martensite do not have time to grow up, so the dispersion is large and the performance is stable. It should be noted that in addition to the design, installation and use of automobile leaf springs, the more important reasons are the heat treatment quality and surface quality. The former refers to the hardness, structure and internal stress; the latter depends on the depth of the surface decarburization layer. It is closely related to heat treatment, so how to achieve non-oxidation heating of steel plates is the first consideration for heat treatment technicians.

(2) During the quenching and heating process, heating temperature, holding time and cooling rate are very important process parameters. If the temperature is too high, the austenite grains will be coarse and the oxidation and decarburization will be serious, which will reduce its strength and fatigue limit. If the temperature is too low, it will cause uneven structural transformation and the appearance of undissolved ferrite, which will also reduce its strength and service life. Therefore, when using high-frequency annealing equipment for heating and heat treatment, the quenching temperature must be strictly controlled.

The quenching heating temperature has a direct impact on the mechanical properties of the steel plate. The best tensile strength, impact toughness and fracture toughness obtained by quenching temperature at 850-900°C. After the steel plate is quenched at about 870°C and formed and tempered, its fatigue life is significantly improved. Therefore, the quenching heating temperature has an important impact on the mechanical properties of the steel plate. The most reasonable temperature range must be determined. Facts have proved that the quenching temperature of 860-880°C is the best , fully meeting its service conditions.

Considering that the loads on automobile spring steel plates are small-energy multiple impacts and fatigue loads, increasing the quenching temperature to obtain lath martensite can increase its tensile strength and fatigue life. However, in order to ensure bending resistance and impact toughness, The quenching temperature should be below 880°C. In addition, according to the specific requirements of the service conditions, it should have strong and tough requirements, so a lower tempering temperature should be used, and the tempering temperature should be 460°C.

(3) At present, the heat treatment method for automobile leaf springs at home and abroad, in addition to conventional overall quenching, has developed an overall induction heating strengthening process, so that the surface layer has a martensite structure of 0.1-0.2mm, and there is a large residual pressure on the surface. stress, which can improve the load-bearing capacity and increase the service life. In addition, the deformation heat treatment process is to perform hot deformation rolling on a roller press after heating the steel plate, and use waste heat quenching treatment to refine the metal, reduce the length and width of martensite, reduce surface decarburization of the steel plate, and improve The surface quality is improved, thereby improving the fatigue life.

After reading the above description, do you have a good understanding of the high-frequency heat treatment process of automobile leaf springs? Of course, if you have any questions during the specific operation, you can consult our technical staff.